More than an hour after his team had climbed to the top of the world Test rankings in an unforgettable, nerve-shredding final session, Graeme Smith was still staring at the tips of the fingers on his left hand.

South Africa's captain, who was leading his country for a record-equalling 93rd time in his 102nd Test, had been put thoroughly, almost sadistically, through the wringer, as Matt Prior counter-attacked thrillingly, and was reprieved first by a Morne Morkel no-ball, then by the third umpire Rod Tucker, who awarded him the benefit of the tiniest doubt in deciding that he had not been stumped.

Smith could almost touch the mace awarded to the world's best Test team with those big fingers. But England, apparently dead and buried at 45 for four, then 146 for six, and 208 for seven, and even 282 for eight, were now within 52 runs of the most improbable victory, one which would have dragged up all the old taunts about South African chokers.

Then Vernon Philander, in his first over with the second new ball from the Nursery End, found Prior's outside edge, exactly as he had done in the first innings. The ball flew low to Smith's left at first slip. "All I keep thinking is it stuck in my left hand," he reflected, sharing a smile with Philander at the winners' press conference in the Lord's Museum. "That catch, that's the one moment. I'm conscious that these three fingers managed to hold on to Matt Prior."

In the stands, Smith's wife Morgan had cradled their tiny baby daughter Cadence, who took her first flight at less than a month old to be here for this special moment, one which South Africa's captain has dreamed of and worked towards for years. The last time his team ascended to the top of those rankings, almost exactly three years ago on 24 August 2009, they did so almost by default, when England regained the Ashes to displace Australia.

South Africa did not even play a game as the world's No1, because before they started their next Test, against England, India had beaten Sri Lanka to take over at the top. They were coached at the time by Gary Kirsten, who is now in charge of South Africa. "Having touched it before we've learned some lessons," said Smith. "We're pretty humble about this whole thing. I don't think there will be too many flashy things happening with our team going forward. The initial achievement is of coming to England and winning 2-0. But the No1 is something we've pushed for, and it will take a few nights for us to reflect on that.

"From a personal perspective, last year was an extremely tough year. So to come back like I have and have these milestones means a lot. I need time to reflect on them."

This time South Africa will be able to take the field as the world's best Test team when they head for Australia for a three-Test series, in which victory would lift Michael Clarke's team to top spot – and possibly dump England down to third, depending on how they do in India. "We've got Australia next and that's going to be an awesome challenge for us," Smith said with relish. "That's the nice thing about international cricket at the moment – there are a lot of outstanding sides. I think there's a real sense of excitement and happiness, but a calmness and a belief, rather than a hope, that we're going to carry it on. We need to have a strong enough base so that when the wind blows, we can handle ourselves."

A message there for England, perhaps, after their inability to preserve top spot.

It was fitting that after Smith caught Prior it should be Jacques Kallis, who had already taken a stunning catch to dismiss Jonathan Trott, who pouched England's last man, Steve Finn, off the next ball. Kallis has been Smith's right-hand man, his rock – no wonder the captain expressed the hope that the 36-year-old can keep going until he turns 40: "If we can keep him off the golf course."

Both Smith and Kallis were bearing messages on their shirts to recognise the long-term role played in South Africa's triumph by wicketkeeper Mark Boucher, an absent friend in this series after he suffered a terrifying eye injury in the opening match of the tour in Taunton. "We miss u Bouch" Smith had written. That was undoubtedly true, but it was typical of the resilience of this group of players, and their inspirational captain, that they found a way to fill the void.